Is hot gas sloshing in a gravitational wine glass—or is astrophysicists’ reasoning going in a circle?

A recent press release explains: “Like wine in a glass, vast clouds of hot gas are sloshing back and forth….” The blue image is assembled electronically from x-ray data and superimposed on the gold image from optical data. Astrophysicists interpret the images in the light of preconceived ideas about gravity and gas. They see a small cluster of galaxies that “smashed into” a larger one, “sloshing” the gas in it. Off-center tidal forces pulled the gas first one way and then another, making it spiral around in the gravity well.............